Electrical sostenuto piano



Feb. 23, 1932. s. COOPER ELECTRICAL SOSTENUTO PIANOS Filed March 25. 1927 IIIIIIIIIIII. llll ll lllll I I I I I I n m" v wwento'c @513 r flbtozwug Patented Feb. 23, 1932 PATENT OFFICE SIMON COOPER, OF BROOKLYN, NEW YORK ELECTRICAL SOST'ENUTO PIANO Application filed March 25, 1927. Serial No. 178,204.

This invention relates to electrical sostenuto pianos; particularly of the type described in United States Letters Patent to me No. 1,598,056, August 31, 1926, in that T electro-magnetic means are employed for the sostenuto and these means are operated by current pulsators directly connected to the strings. The operation of each such pulsator, in the patented arrangement, depends upon the relative motion between the two electrodes, one of which is directly connected with the string which it controls; and, according to said arrangement, various adjustments of the pulsators, as regards their relation to the strings, the Weight and inertia of the electrodes, etc., are depended on to effect a proper synchronization of the pulsators with the strings.

Said adjustments necessarily are difficult,

- require considerable skill and must be determined to a large extent empirically.

One of the objects of the present invention is to provide a method of and means for in- M H suring dependable sostenuto without troublesome empirical adjustments.

Again, if the vibration of a string is to'be sustained to give sostenuto, the intermittent pulls of the magnet on the string must be timed to agree with the natural vibratory movements of the string toward the magnet.

In this connection, it must be rememberedthat apiano string, even in the bass scale, is vibrating quite fast; and this speed of vibration reaches a very high frequency at the treble scale of strings. Now, all previous pulsators have two electrodes which make contact with each other or have between them some conductor such as carbon pencils, balls or granules, and current flowing through the pulsator or transmitter is caused to fluctuate by the varying pressure of contact of the electrodes on each other or on the conducting medium between them. All commercial pulsators have one of the electrodes suspended by means of a diaphragm, and the other electrode fixed as by resting upon the electrode suspended by the diaphragm. This suspended diaphragm will have its natural period or frequency of vibration, yet it will 00 be readily understood that unless this natural frequency is equal to or a sub-multiple of the frequency of the string vibration, there will be no possibility of obtainng current pulsations which match properly the string vibration.

Another object is to provide a method of and means for insuring dependable sostenuto, as above; and by the use of a pulsator vibrating at the rate, or at a rate corresponding to a sub-multiple, of the rate of free vibration of the string, thereby to utilize my discovery that a pulsator so vibrating, provided another difficulty is disposed of, is capable of true sostenuto.

Accordingly, a further object is to provide a method and means, as already stated, and also a method and means of taking care of the difiiculty just referred to, the distortive or destructive effect of a part of the pulsator or its support vibrating according to its own natural period of vibration.

These various objects of the invention are attained by making the pulsator in effect non-resonant as regards the string. This I may accomplish in a commercial way b attaching one of the electrodes of the pulsator to the string by a rigid mechanical connection, as in said patent, and by supporting the other electrode on or by means of a nonresonant medium. Preferably, one of said electrodes is relatively massive, so that inertia is a factor; and, consequently, it is also preferred to have the electrode supported in the non-resonant medium the relatively massive one.

I find that when a pulsator has one of its electrodes nonresonant, or supported by a non-resonant medium, and the other electrode mechanically connected to the string, all difficulties are overcome, and the pulsator is synchronized for sostenuto while vibrating at the rate, or at a rate corresponding to a submultiple of the rate, of free vibration of the associated string.

I find also that then, the transverse movement of the string, even where the connection is made at a point nearer one bridge support than the other to hold down interference with the natural motion of the string, vibrates the pulsator to cause relative motion of the elecyrs trodes which may be depended on for sostenuto synchronization, and true sostenuto.

It is true, of course, that during the rapid vibration of the fixed or string-connected electrode and say the granular carbon mass between the electrodes, the fixed electrode moves with each motion of the string .toward and from the non-resonant electrode, resulting in a number of rapid impacts on the latter. On the other hand, the non-resonant electrode is on a sluggish non-resonant mount or support; and the motion of the non-resonant electrode, relative to the other electrode and the granular filling, I find, is comparatively slight, particularly on the higher pitched note strings; occurs a less number of times per. second, and occurs at a rate corresponding to a sub-multiple of the rateof free vibration of the string. The action might be illustrated by considering the non-resonant electrode as an anvil on which light hammer blows are successively struck, the inertia of the anvil preventing a displacement of itself as quickly or as often as the blow is struck. 7 Further, I find that such displacement occurs, with an accompanying current pulsation, and an accompanying pull on the string by the magnet, after every so many string vibrations, and each such pull on the string is exerted only while the string is moving towardthe magnet. Thus is attained dependable sostenuto, and yet troublesome empirical adjustment-of the pulsator is not a factor. At the same time, I find that since one of the electrodes at least is not supported by a means or medium capable of exhibiting its own natural period of vibration, no deleterious variations in the current pulsations occur, and so true sostenuto, also, is attained. Another object of the present invention is to overcome a serious trouble in previous microphones as attempted to be used for electrical sostenuto in pianos. This trouble arises from the disintegration of the contact surfaces of the carbon elements dueto mechanical abrasion and arising as a result of incandescence or even arcing at or across the points of contact. 7

According to the present invention, T pro vide, in a pulsator having a non-resonant mount for one of the electrodes, a collection of carbon granules or the like arranged'or retained in such manner as to offer what may be termed self-renewing contact surfaces or points.

Another object of the present invention is to provide a method of arranging the con nection between a piano string and one of the electrodes of the controller or pulsator for that string, whereby interference withthe natural motion of the string will be held down considerably, and at the same time the pulsator will be operated for true sostenuto according to the invention. I have discovered that suchoperation may be had when said connection, as a mechanical one, is made at the string very close to oneof the bridge supports of the latter, or even at a non-singing portion of the string; and, also, that the pulsator will function usefully according to the invention when attached to the sounding board, and, in some instances when attached to the pianoframe.

Still another object of the invention is to provide an electrical attachment for a piano string having parts so connected to and associated with thestring that the electrical sostenuto may act primarily or accentuatingly in. regard to a tone made up of a desired combination of the fundamental and its harmonics. v

In the accompanying drawings, to which reference will now be had, several different illustrative forms of the invention are shown; but these forms are, as just stated, of course merely illustrative, and not to be taken as in any sense defining or limiting the invention itself.

Fig. 1 is a diagrammatic view illustrating one form of circuit and possible ,relationsof the actuating magnet and controlling pulsator to a piano string.

Fig. 2 is a longitudinal vertical section of the form of pulsator shown in'Figr 1, illustrating. also a type of auxiliary support.

Fig. 3 shows the pulsator of Fig. 2 in perspective.

Fig. dis view similar to Fig. 2, but showing a different form of pulsator and a different support therefor.

Fig. spective.

Fig. 6 shows partly in top plan and partly in section still another form of pulsator according to the invention.'

.100 5 shows the pulsator of Fig. 4 in per- Fig. 7 shows in vertical section, still another form.

Fig. 8 is a sectional view of still another form.

In Fig. 1, one of thepiano strings is indicated at 10, stretched over the bridge pieces 11, 12. 13 indicates the electro-magnet for vibrating the string and 14 the pulsator for controlling said magnet, said pulsator being located in a circuit with the magnet, which circuit includes a suitable source of energy 15 and a switch 16 operated by the piano key 17 The pulsator comprises in each instance a pair of cooperating electrodes 18 and 19 with an interposed mass 20 of carbon granules or the like. One of these electrodes 18 is rigidly connected with the piano string by means v consisting in the case of Figs. 1, 2 and 3, of a bar or rod 21 shown as having a forked end 22 which is forced over the piano string, said bar having secured thereto a sleeve 23offibre or the like in whichthe electrode is affixed. The companion electrode 19 is loosely contained in an envelope; of felt, wool yarn I or the like which fits inside the sleeve or thimble 23 so as to hold the electrode in proper relation to the granular mass, a wrapping of yarn 25 being provided to hold'the outer portion of the envelope to the supporting bar and a pad 26 of felt being shown as interposed between the outer end of the envelope and the bar as a further cushioning medium.

The non-resonant electrode 19 is relatively heavy; in other words, is of suflicient mass to give it such inertia that it will operate in effect as an anvil for the lighter, directly actuated hammer electrode, and being supported as it is in a non-resonant envelope, its motion, relative to the other electrode, is slight and of less frequency.

The electromagnet is supported so as to operate directly on the string, which is made susceptible to magnetic attraction, and the effect of this pulsator is to keep the force of the electromagnet in phase with the motion of the string, in the sense that each pull of the magnet on the string occurs while the string is moving toward the magnet, so that the vibration of the string is sustained and the string is caused to emit its true musical tone.

The outer end of the pulsator may be supported as by suspending it with a cable 27 from a baror bridge 28. Then it is possible to raise or lower the free end of the pulsator without changing its point of connection with the piano string. The raising or lowering of the connection tips up or down the free end of the pulsator and correspondingly affects the conductivity of the granular mass. These adjustments obviously will have an effect on the operation of the pulsator and may be used where some adjustment is necessary to bring the pulsator into synchronous relation with the string.

Figs. 4 and 5 illustrate a somewhat simplified form of pulsator in which both the electrodes are encased in a common non-resonant envelope 32 of felt or the like and the stringvibrated electrode is connected with the string by an arm 33 directly secured thereto as by means of a screw 34 and having a notched end as before to clamp on the string. The screw 34 may be used as the terminal screw for the vibrated electrode and the nonresonant electrode may have a terminal screw 35, these being similar to the terminal screws provided in the first form of the invention.

In the form of the invention disclosed in Fig. 6, there is a sleeve or thimble 36 similar to the sleeve 23 used in'the first form shown, except that in this instance it encloses both electrodes, the non-resonant support for the heavier electrode being provided in this case by a loose wrapping 37 of yarn or the like intel-posed between the anvil electrode and the surrounding sleeve or shell. Another feature of this form is that the arm 38 which is notched to connect with the string is formed as an integral extension of the shell. The form of the invention shown in Fig. 7 differs from the form disclosed in Fig. 2 principally in that a pad 39 of felt or other non-resonant material is interposed between both electrodes and the supporting bar 21.

The form of pulsator shown in Fig. 8 has a thimble or shell 28, of fibre or the like, sleeving both electrodes as in Figs. 2, 6 and 7 but in the present case the more massive electrode 19' is connected to the piano string as by screw-pin 29, shaped to present at its free end a flat blade notched as indicated at 29a. The screw-pin may carry a nut (not shown) to take the endof a wire in the circuit containing current source 15; the other electrode 18 carrying a screw 18a for a similar connection. The non-resonant envelope is indicated at 30.

One of the important features of the present invention, graphically shown in F 1g. 8 at 31, and preferably present in all forms of the invention, is that the body of carbonaceous or other suitable granular conducting material is loosely confined between the electrodes so as to be free to move for the purpose of automatically and from time to time presenting new conducting surfaces and new contacting points.

The pulsator is preferably attached to the string at a point Where the loop of the freely vibrating string will assist in causing the magnet to attract the string at times when the string is moving toward the magnet. This point of attachment may be determined by experiment and is usually found to be somewhere about the upper supporting bridge.

During vibration of the piano string, motion is imparted to the fixed electrode, the granular conducting mass, and, in a retarded fashion, due to the interposition of the nonresonant element, to the electrodes supported on said elements; while, due also to the presence of said element, true sostenuto is not at all interfered with by any part of the pulsator or its support vibrating in accordance with its own natural frequency of vibration, at least so far as the car can determine.

At the same time, the relative motions of the electrodes result in alternate compression and release of the carbon granules or pellets as between themselves and the faces of the electrodes, producing variations in circuit resistance proportional to and in time with the vibrations of the string; and the magnet, being under control of the pulsator, is actuated accordingly to maintain the string in vibration so long as the controlling switch is closed.

Such actuation of the pulsator, where the carbon granules are not imniovably confined, results in a slow circulation of the granules a in"- the; space between the; electrodes.- As the amplitude. of. vibration. increases :or the number-ofvibrationszper-second is great er, or both, circulatory' movement of the granulesais more, pronounced. If. the amplitude-of vibrationuis small,- eventhough-the: number .1 of vibrations per second -;is quite 1 high, the circulatory movement is comparativel-yslow. Under both conditions, however-,; the relation of the granules to each other-1; and; the relation. of the granules; in contact withrthe'electrodes follows a progressive' action, automatically renewing the con-1' tact surfaces whenever the piano string is in vyibratiOn.

I have discovered that. 1 it is highly. desirable. if not essential to synchronize the energization of the magnetiwith the. motion of-the. string, insuch wise that the magnet ;is energized at a moment which will attract the string. at: a particular point in' its path ofr'vibratiomso thatrthe? vibratile formation of the'.. string.iwhichlmust.existto sound the note :and the. harmonics desired is'not disturbed bythe application of the. magnetic force. In sounding a piano string,,the requirement .is that a fundamental and cer-' tain harmonics of that fundamental be audi-. ble, and. that certain other fundamentals -.which are unharmonic with the first funda mental be deadened. T, In some piano actions, for'instance, the hammer (indicated at. H in Fig; l) .is caused to strike-the string at one-v seventh or one-ninth; of "itstlength, :such a JqblOW; oreventin the. formation of a: node at-the. point-struck and so damping .or de stroying the seventh or ninth harmonic. It should be. pointed out, as my experiments apparently demonstrate, that while the magnet exerts a small magnetic pluck on the string,;the magnetic attraction'is not con-. fined to a point but is rather stretched over a zone in the-length of the string. :Also, the magnetic attraction is not staccato or in the nature of a blow,:but rather is a force wave,

essential to best musicalresults, thatz'is, tov

sound the fundamental and such harmonics as .are desired while holdmg'down the un:

desirable harmonics.

I find that the structure shown in Fig; 7 isparticularly desirable :where it is wished to secure a more-mellow and less sharp tone than that produced with say the form-of Fig. 2.. In all the forms shown; however, the nonresonant method of -supporting oneaof the electrodes enables said electrode toadj ust lll'm self. to a periodic'vib'ratiomtimed to, and a fering with the natural vibration of the string.

Inasmuch as many-changes could'be made in the above constructions, and many apparently widely different embodiments ofmy from the scope thereof, it is intended that all matter contained in theabove description or shown in the accompanying drawings shall. e. interpreted as illustrative and not in. a limiting sense.

It is also to be'understood that the language contained in the following claims isintended to cover all the generic and specific features of. the. invention herein described and all statements;- of the :scope of the invention which, as a matter of language, might be said to fall therebetween. V What I claim is 1. In a device of the kind described, a-vi-- brato'ry string.- a pulsator comprisingan elec-,

7 5 inventioncouldbe made wlthout departing trode rigidly connected with the string and a cooperatingelectrode of greater mass than the first, means for supporting the cooperating electrode in.non-resonant-relation to the vibratory string, and a magnet for vibrating the string-controlled'by said pulsator.

2. Ina device of the kind described, a vibratory string. a Dulsator comprising an electrode rigidly connected with the string and 100 a cooperating electrode, means for support Ving'the cooperating electrode in non-resonant relation to the vibratory string, and a magnet for vibratingthe string controlled by said pulsator.-

3. In a device of the kind described, a vibra'tory string, a magnet for vibrating :the same; and a controller for said magnetcomprising cooperatingelectrodes, one relatively light and rigidly connected with the vi bratory string and the other relatively heavy,;

and means for supporting the. cooperating electrode in non-resonant relation to the string. v

4. In a device of the kind described, a vibratory string, a. magnet for vibrating the same and a controller for said magnet including a member rigidlvc'onnected with the str1ng,an electrode mechanlcally connected with said member, -a-cooperat1ng electrode and a non-resonant support forsaid second electrode.

5." In a device of the kind described, a vi- I bratory string, a magnet for vibrating the same anda controller for said magnet including a member rigidly connected with thestring, an electrode mechanically con-' nected with said member, a cooperatingelee trode and a non-resonant supportof felt-like materialzforv said second electrode;

6. In a device of the kind described, a vibratory string, a magnet for vibrating the same and a controller for said magnet including a member rigidly connected with the string, an electrode mechanically connected with said member, a cooperating electrode, and a non-resonant support for said second electrode and interposed between said electrode and the string engaging member aforesaid.

7. A pulsator for the purpose described comprising a member for rigid engagement with a vibratory string, an electrode connected with said member, a cooperating elec trode, and a non-resonant support interposed between said cooperating electrode and the member aforesaid.

8. A pulsator for the purpose described comprising a member for rigid engagement go with a vibratory string, an electrode rigidly fixed to said member, a cooperating electrode, and substantially non-resonant means for supporting said second electrode on said member.

9. A pulsator for the purpose described comprising a member for rigid engagement with a vibratory string, an electrode rigidly fixed to said member, a cooperating electrode, and a substantially non-resonant sleeve for 80 supporting said second electrode on said member.

10. In a device of the kind described, a sup port provided with means for connecting the same with a vibratory string, a sleeve carried 85 by said support, an electrode in said sleeve,

acooperating electrode in said sleeve, and an envelope of non-resonant material about one of said electrodes.

11. In a device of the kind described, a support provided with means for connecting the same with a vibratory string, a sleeve carried by said support, an electrode fixed in said sleeve, a second electrode of greater mass than the first, a mass of variable conductivity between the electrodes, and a non-resonant supporting medium for the electrode of greater mass.

12. In a device of the kind described, a support provided with means for connecting the same with a vibratory string, a sleeve carried by said support, an electrode fixed in said sleeve, a second electrode of greater mass than the first, a mass of variable conductivity between the electrodes, and a non-resonant supporting medium for the electrode of greater mass and comprising an envelope of feltlike material surrounding said electrode and extending within the sleeve aforesaid.

13. In an electric sostenuto piano, a vibratory string, a magnet for vibrating the same, and a pulsator in circuit with said magnet comprising an electrode rigidly connected with the string, a non-resonant element, and a cooperating electrode connected with the string through said element.

14. The herein disclosed means for producing a sostenuto efl'ect in a vibratile string which comprises a pulsator supported directly on the vibratile string, said pulsator including spaced electrodes, means connecting one of the electrodes of said pulsator rigidly with the string, means supporting the companion electrode by a non-resonant medium and a magnet for vibrating the string controlled from said pulsator.

15. In a device of the kind described, the combination of a support provided with means for mechanically attaching the same directly to a vibratory string, a pulsator on said support including relatively movable electrodes and a mass of granular conducting material interposed between said electrodes, and means for adjusting the inclination of said support to vary the action of said electrodes on said mass.

16. In a device of the kind described, the combination of a support provided with means for mechanically attaching the same directly to a vibratory string, a pulsator on said support including relatively movable electrodes and a mass of granular conducting material interposed between said electrodes, means for non-resonantly supporting one of said electrodes on the support, and auxiliary supporting means for the pulsator adjustable to vary the action of said electrodes on said mass.

17. In a device of the kind described, the combination of a support provided with means for mechanically attaching the same directly to a vibratory string, a pulsator on said support including relatively movable electrodes and a mass of granular conducting material interposed between said electrodes, and suspensory means for a part of said support removed from its point of engagement with the string.

18. In a device of the kind described, the combination of a support provided with means for mechanically attaching the same directly to a vibratory string, a pulsator on said support including relatively movable electrodes and a mass of granular conducting material interposed between said electrodes,

and means for adjustably inclining said support to the horizontal and to cooperate with said support in sustaining said'pulsator opposite a predetermined point along the length of the string.

19. In a sostenuto piano, an electric controller comprising a pair of cooperating relatively movable electrodes arranged with a chamber between opposing surfaces thereof, a granular conducting body loosely confined in said chamber between said surfaces to thereby enable circulation of the individual granules to continually create fresh contact surfaces between the granules and between said granules and the electrode surfaces, a direct mechanical connection for attaching one of the electrodesto'apiano string, and nonresona-ntmeans for: supportingv the com-' -panionelectrode from said first electrode.

. .20.. In an -electricalsostenuto device for i5 pianos,-the combination of apiano'string, a .,.pu. lsatorhav1ng a plurality of relatively movableielectrodeslone ofewhicli is connected nmecha-nically to the string, said; mechanical trode of the pulsator.

$21.? Themeans definedinelaim l l, which. .alsoincludes-rigid means connecting the firstv mentionedelectrode to .the string at apoint a .-at-..or.-near onerof the supporting bridges to cause-the: magnetto act on the string to: pro- A duce apredetermined musical'tonmby sound-- .'ing\the desired fundamental :andharmonics 2 only.

-the desireda fundamental and rharmonics, to obtain predetermined:musicaltone, which 5 consists: in. magnetically plucking the :string' .aatsuch-point: asitoz accentuate 1 only -.the' de- .2: sired fundamental and harmonics. 23. In" an electric .sostenuto; T piano: :action,

- :the combination ofi a current'pulsator' for s causing current fluctuation qopenasted by the -vibrat-ionzof the'is'tring. and. including a plurality of relatively movable electrodes,a mag- Jofitsinass for E causing: sucli fluctuation. lw24ealn anwelectric SOSlEGIllltQPlLIlO -action, mthe- =COIl1bl11-21t1011 of a: current pulsator' oper- 40". .ated by-the :vibration ofithe stringand includ- I i .1.- ing'. a. plurality; I of :relatively. amova-ble: 16160- thee-string; and :means' "for. maintaining true -;--sostenuto during :current: fluctuation of a "freqnency Which-;-is a-zsub-multiplexof the frequency' of vibration of..the'.string; said: means i a; r including a' non;-vibratory.= mountifor one of the; electrodes.

by the vibration ,ofthe :string andincluding a magnet forsimparting:sostenuto-to tliestring,

and means for maintaining.itrueasostenuto ssrandunclurling .means on maintaining .one of the electrodes. devoid: "of any; natural pitch of zvibration. V 3- -26: Inuan.electriczsostenuto piano, a. pulsisator; ancbmeans for: securingsaid pulsator to. -a-=:string,isaid means-providing a mount for nt'lierpulsator including a :forked element for gripping-iengagementmvith the string.

.1: 27;? Inxan. electric sostenuto piano,. a pul- "mi-strin *tSflld'lIlGihIlStlIlGllldlIl a'su ort carwsaton; and rmeansifor securing'saidpulsator to tend HIGHIISQf-IEOI" COIlIlECtlOIl ito; a avibratory a pulsator including a first electrode directly wibrated by string vibration and asecond electrode so massive. as to be directly unaffectedby spring vibration.

29. In an electric sostenuto system for pi- 13/110S7 an electric current undulating device-on acstring, means'forconnecting said device to said-string at aboutone-of its bridge sup:

5 ports, and means for suspending the device from a support isolated.- from sympathetic oivi-bration with the string.

, Apulsator-for purposes: set' forth, .com-

7 o 1 prising an electrode of moderate mass, means; 35 22.; Theiherein' disclosed processof produc-p ng aisosten-uto effect Wh-ile-accentuating only substantial mass, comminuted conducting material between adjacent ends ofthe electrodes, and: non-resonant material surrounds a ing and supporting thewsecond electrode in relation-to the first.

31.. A- pulsator for purposes set forth, comuprising an electrodeof moderate-mass, means 'plOVlCllllg't a: practically Tclirect -mechamcah connection of the electrode to a vibratory -"stri-ng,=a second electrodezofrelatively greater eanetforiiinparting sostenuto to the string, and, means formaintaining true; sostenuto. and in-'. V 5.;cluding a: mount for one ofathe electrodes to: maintain tha-tre'lectrode subject to the-inertia;

relation vto zthe first.

v 32. A pulsator for purposes setfo'rth, com- P181110 a 1 su ortrn member: havin at one p a a a:

i end .means'. for TCQIlIlQCtlOIl. tow a iVilOIZLtOIYg w, "strin trodes, a magnet for impartlngisostennto to;

atsleevethereon, a first electrode of moderate mass held in said sleeve, a second select-rodeof substantial :mass having a: part ivithinlthesleeve,comminuted.conducting material confinedinthe sleeve betweenethe elem-s i m :trodes, and a sleeve ofnon-resonant'material surrounding the second electrodei'and supg Y 1 porting it in relation to the first namedisleeve. 1,125.; In an '-.e-lectr1c- SOStQIlUtOPlELIIO action, 50 combination of. a current pulsator operated 1 33;-'A =pulsator :t'orpurposes set forth, comprising substantially rigid supporting;

v V memberhaving at one end means for conplurality of "relatively movable electrodes, a

nectionto a vibratory string, a sleeve thereon, afirst electrodeof moderate mass held in said sleeve, asecond electrode of relatively greater mass having a partwithinthe sleeve; comminuted conducting materi al confined in the sleeve between the electrodes, and asleeve of substantially resilient, non-resonant ma- -.terialsurroundingthe second electrode and suppiorting itzin :relation to -theifirst. named:- sleeve. V

-z-34.. 1A pulsator for purposes set'forth,;comprising. a supporting. memberg'having: at one string, a sleeve thereon, a fiI-Si'LGlBCtI'OdBE-Of moderate mass held in said sleeve, a second electrode of substantial mass having a part within the sleeve, comminuted conducting material confined in the sleeve between the electrodes, a sleeve of non-resonant material surrounding the second electrode and supporting it in relation to the first named sleeve, and non-resonant cord Winding securing the non-resonant sleeve to the support.

35. A pulsator for purposes set forth, comprising a substantially rigid supporting member having at one end means for connection to a vibratory string, a sleeve thereon, a first electrode of moderate mass held in said sleeve, a second electrode of relatively greater mass having a part within the sleeve, comminuted conducting material confined in the sleeve between the electrodes, and a sleeve of substantially resilient, non-resonant material surrounding the second electrode and supporting it in relation to the first named sleeve, and non-resonant cord winding securing the non-resonant sleeve to the support.

36. A pulsator for purposes set forth, comprising a supporting member having at one end means for connection to a vibratory string, a sleeve thereon, a first electrode of moderate mass held in said sleeve, a second electrode of substantial mass having a part within the sleeve, comminuted conducting material confined in the sleeve between the electrodes, a, sleeve of non-resonant material surrounding the second electrode and supporting it in relation to the first named sleeve, and non-resonant material interposed between the support and said sleeves.

37. A pulsator for purposes set forth, com

prising a substantially rigid supporting member having at one end means for connection to a vibratory string, a sleeve thereon, a first electrode of moderate mass held in said sleeve, a second electrode of relatively greater mass having a part within the sleeve, comminuted conducting material confined in the sleeve between the electrodes, a sleeve of substantially resilient, non-resonant material surrounding the second electrode and supporting it in relation to the first named sleeve, and non-resonant material interposed between the support and said sleeves.

38. A pulsator for purposes set forth, comprising a supporting sleeve, means for connecting one end of the sleeve to a vibratory string, a first electrode of moderate mass and held in the sleeve near one end thereof, a second electrode of substantial mass within the sleeve, comminuted conducting material confined in the sleeve between the electrodes, and non-resonant material supporting the second electrode in'the sleeve.

39. A pulsator for purposes set forth, comprising a supporting sleeve, means for connecting one end of the sleeve to a vibratory string, a first electrode of moderate mass and held in the sleeve near one end thereof, asecond electrode of relatively greater mass within the sleeve, comminuted conducting material confined in the sleeve between the electrodes and non-resonant material supporting the second electrode in the sleeve.

40. A pulsator for purposes set forth, comprising a supporting sleeve, means for connecting one end of the sleeve to a vibratory string, a first electrode of moderate mass and held in the sleeve near one end thereof, a secone electrode of substantial mass within the sleeve, comminuted conducting material confined in the sleeve between the electrodes, and a non-resonant wrapping about the second electrode and supporting it within the sleeve.

41. A pulsator for purposes set forth, comprising a supporting sleeve, means for connecting one end of the sleeve to a vibratory string, a first electrode of moderate mass and held in the sleeve near one end thereof, a second electrode of relatively greater mass within the sleeve, comminuted conducting material confined in the sleeve between the electrodes, and a wrapping of non-resonant cord about the second electrode and supportin it Within the sleeve.

in testimony whereof I aflix my signature.

SIMON COOPER. 

